"We are in serious ecological overshoot, consuming resources faster than the Earth can replace them," WWF International Director General James Leape said. "The consequences of this are predictable and dire."

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Eventually, ecological assets, such as forests and fisheries will be harvested to such a degree that they might disappear altogether. In 2003, 25 percent more natural resources were used than the Earth could sustainably replenish, the report said.

According to the WWF, humanity's ecological footprint — measuring the area of biologically productive land and sea required to provide all the resources used and absorb waste — has more than tripled between 1961 and 2003.

Countries with the largest ecological footprint per person are the United Arab Emirates, the United States, Finland, Canada, Kuwait, Australia, Estonia, Sweden, New Zealand and Norway. China is ranked 69th, but its size and rapid economic growth make it a key player for the sustainable use of the world's resources, the report said.

Another indicator of the strain on natural ecosystems is the decline of about one-third observed in more than 1,300 vertebrate species around the world between 1970 and 2003, said the WWF. The loss of natural habitat to cropland and pasture has been particularly acute in the tropics, the report said.